141 lines
4.5 KiB
Python
141 lines
4.5 KiB
Python
import hashlib
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import hmac
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import os
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import posixpath
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import secrets
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import typing as t
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if t.TYPE_CHECKING:
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pass
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SALT_CHARS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
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DEFAULT_PBKDF2_ITERATIONS = 260000
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_os_alt_seps: t.List[str] = list(
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sep for sep in [os.path.sep, os.path.altsep] if sep is not None and sep != "/"
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)
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def gen_salt(length: int) -> str:
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"""Generate a random string of SALT_CHARS with specified ``length``."""
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if length <= 0:
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raise ValueError("Salt length must be positive")
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return "".join(secrets.choice(SALT_CHARS) for _ in range(length))
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def _hash_internal(method: str, salt: str, password: str) -> t.Tuple[str, str]:
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"""Internal password hash helper. Supports plaintext without salt,
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unsalted and salted passwords. In case salted passwords are used
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hmac is used.
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"""
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if method == "plain":
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return password, method
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salt = salt.encode("utf-8")
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password = password.encode("utf-8")
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if method.startswith("pbkdf2:"):
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if not salt:
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raise ValueError("Salt is required for PBKDF2")
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args = method[7:].split(":")
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if len(args) not in (1, 2):
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raise ValueError("Invalid number of arguments for PBKDF2")
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method = args.pop(0)
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iterations = int(args[0] or 0) if args else DEFAULT_PBKDF2_ITERATIONS
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return (
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hashlib.pbkdf2_hmac(method, password, salt, iterations).hex(),
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f"pbkdf2:{method}:{iterations}",
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)
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if salt:
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return hmac.new(salt, password, method).hexdigest(), method
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return hashlib.new(method, password).hexdigest(), method
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def generate_password_hash(
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password: str, method: str = "pbkdf2:sha256", salt_length: int = 16
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) -> str:
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"""Hash a password with the given method and salt with a string of
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the given length. The format of the string returned includes the method
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that was used so that :func:`check_password_hash` can check the hash.
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The format for the hashed string looks like this::
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method$salt$hash
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This method can **not** generate unsalted passwords but it is possible
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to set param method='plain' in order to enforce plaintext passwords.
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If a salt is used, hmac is used internally to salt the password.
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If PBKDF2 is wanted it can be enabled by setting the method to
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``pbkdf2:method:iterations`` where iterations is optional::
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pbkdf2:sha256:80000$salt$hash
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pbkdf2:sha256$salt$hash
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:param password: the password to hash.
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:param method: the hash method to use (one that hashlib supports). Can
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optionally be in the format ``pbkdf2:method:iterations``
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to enable PBKDF2.
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:param salt_length: the length of the salt in letters.
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"""
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salt = gen_salt(salt_length) if method != "plain" else ""
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h, actual_method = _hash_internal(method, salt, password)
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return f"{actual_method}${salt}${h}"
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def check_password_hash(pwhash: str, password: str) -> bool:
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"""Check a password against a given salted and hashed password value.
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In order to support unsalted legacy passwords this method supports
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plain text passwords, md5 and sha1 hashes (both salted and unsalted).
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Returns `True` if the password matched, `False` otherwise.
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:param pwhash: a hashed string like returned by
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:func:`generate_password_hash`.
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:param password: the plaintext password to compare against the hash.
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"""
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if pwhash.count("$") < 2:
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return False
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method, salt, hashval = pwhash.split("$", 2)
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return hmac.compare_digest(_hash_internal(method, salt, password)[0], hashval)
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def safe_join(directory: str, *pathnames: str) -> t.Optional[str]:
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"""Safely join zero or more untrusted path components to a base
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directory to avoid escaping the base directory.
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:param directory: The trusted base directory.
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:param pathnames: The untrusted path components relative to the
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base directory.
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:return: A safe path, otherwise ``None``.
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"""
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if not directory:
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# Ensure we end up with ./path if directory="" is given,
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# otherwise the first untrusted part could become trusted.
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directory = "."
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parts = [directory]
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for filename in pathnames:
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if filename != "":
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filename = posixpath.normpath(filename)
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if (
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any(sep in filename for sep in _os_alt_seps)
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or os.path.isabs(filename)
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or filename == ".."
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or filename.startswith("../")
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):
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return None
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parts.append(filename)
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return posixpath.join(*parts)
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